Stage system, exposure apparatus, and device manufacturing method

ABSTRACT

A stage system that can meet enlargement of a stroke and thus, particularly, that can be suitably incorporated into an electron beam exposure apparatus. The stage system includes a first fixed guide having a plane along X and Y directions, a first movable guide to be guided by the first fixed guided (the first movable guide having a Y guide  3   f  extending in the Y direction), a second fixed guide having a plane along X and Y directions, a second movable guide to be guided by the second fixed guide (the second movable guide having an X guide extending in the X direction), and a central movable member to be guided in the X and Y directions by the Y guide and the X guide.

This application is a divisional application of copending U.S. patentapplication Ser. No. 10/862,383, filed on Jun. 8, 2004.

FIELD OF THE INVENTION AND RELATED ART

This invention relates to a stage system to be used in various measuringinstruments, or in a projection exposure apparatus, for a semiconductorlithography process, for moving and positioning a substrate, such as awafer, at a high speed and with a high precision. The stage system ofthe present invention is best suited for a stage system particularly tobe used in an electron beam exposure apparatus, in which an electronbeam is used to perform pattern drawing for direct patterning of a waferor reticle exposure, or in an EUV (extreme ultraviolet) exposureapparatus using EUV light as exposure light in which the stage system isused in a vacuum ambience.

The manufacture of devices such as semiconductor devices, for example,is based on lithography technology in which various patterns formed on amask are transferred to a wafer in a reduced scale, by use of light.Extremely high precision is required in relation to the mask pattern tobe used in such lithography technology, and an electron beam exposureapparatus is used to make such a mask. Further, an electron beamexposure apparatus is used also in a case wherein a pattern is to bedirectly formed on a wafer without using a mask.

As regards such an electron beam exposure apparatus, there is a pointbeam type apparatus wherein an electron beam to be used is shaped into aspot-like shape, and a variable rectangle-beam type apparatus wherein anelectron beam has a rectangular section of various size, for example. Inthese types of exposure apparatus, however, generally, the apparatuscomprises an electron gun unit for producing an electron beam, anelectron optical system for directing the produced electron beam to asample, a stage system for scanningly moving the whole surface of thesample with respect to the electron beam, and an objective deflector forpositioning the electron beam upon the sample very precisely.

The region that can be positioned by use of an objective deflector hasonly a small size of about a few millimeters, to suppress the aberrationof the electron optical system as much as possible. To the contrary, asregards the size of the sample, for a silicon wafer, it is about 200-300mm in diameter, and for a glass substrate to be used as a mask, it isabout 150 mm square. So, the electron beam exposure apparatuses includea stage system by which the whole surface of the sample can be scannedwith the electron beam.

In electron beam exposure apparatuses, since the positioning response ofthe electron beam is extraordinarily high, generally, they use a systemin which the attitude of the stage or a positional deviation thereof ismeasured and the measured value is fed back to the positioning of theelectron beam through the deflector, rather than attempting to improvethe mechanical control characteristic of the stage. Also, since thestage is disposed in a vacuum chamber and, furthermore, there is arestriction that a change in a magnetic field that may influence thepositioning precision of the electron beam must be avoided, generally,the stage is disposed by use of a limited element of a contact type,such as rolling guides or ball screw actuators.

Such contact type elements involve a problem of lubrication and dustcreation, for example. Japanese Laid-Open Patent Application No.2002-252166 shows a countermeasure therefor, and FIG. 10 illustrates it,that is, a stage having two freedoms of movement in a planar direction,using vacuum air guides and linear motors. In the example of FIG. 10,very smooth acceleration can be accomplished and, yet, with respect tothe positioning direction, external disturbance from the guide is verysmall. In the illustrated example, the stage comprises an X slider, a Yslider and an X-Y slider, wherein the X slider and the Y slider areconfined with respect to rotation about the Z axis, by means of radialbearings.

FIG. 11 shows an example of a stage, to be used in an atmosphere,corresponding to a stage disclosed in Japanese Laid-Open PatentApplication No. 2002-8971. In the example of FIG. 11, like the exampleof FIG. 10, the stage comprises an X slider (X guide bar 28), a Y slider(Y guide bar 29), and an X-Y slider, but the X slider and the Y sliderare not confined with respect to rotation about the Z axis.

As regards the election beam exposure apparatus, there is a knownexample disclosed in Japanese Laid-Open Patent Application No.H09-330867. In the apparatus of this document, a plurality of electronbeams are projected upon the surface of a sample along designcoordinates and the electron beams are deflected along the designcoordinates to thereby scan the sample surface. Additionally, inaccordance with a pattern to be drawn, the electron beams areindividually turned on and off to thereby draw the pattern. In such amultiple electron-beam type exposure apparatus, a desired pattern can bedrawn by use of plural electron beams, and thus, the throughput can beimproved.

FIG. 12 illustrates a general structure of a multiple electron-beam typeexposure apparatus. Denoted at 501 a, 501 b, and 501 c are electron gunsby which a plurality of electron beams can be individually turned on andoff. Denoted at 100 is a reduction electron optical system for reducingand projecting the electron beams from the electron guns 501 a, 501 band 501 c, onto a wafer 305. Denoted at 306 is a deflector for scanningthe plural electron beams projected to the wafer 305.

FIG. 13 illustrates the action as a wafer is scanned with pluralelectron beams, in the exposure apparatus of FIG. 12. White smallcircles depict beam reference positions BS1, BS2 and BS3 whereat theelectron beams are incident, as they are not deflected by the deflector306. These beam reference positions BS1-BS3 are placed along a designorthogonal coordinate system (Xs, Ys).

On the other hand, the electron beams are scanned (scanningly deflected)also along a design orthogonal coordinate system (Xs, Ys) while takingthe beam reference positions as a reference, to scan associated exposurefields EF1, EF2 and EF3, respectively. In this stage, the stage whichcarries the wafer 350 thereon is scanningly moved mainly in the Ydirection, as denoted at 200 in FIG. 13, to perform sequential exposuresof zones of the wafer.

SUMMARY OF THE INVENTION

Enlargement of the wafer diameter has been required in lithography, andthus, the stroke of the apparatus should be enlarged. In the example ofFIG. 10, there is a difficulty in setting the orthogonality of confiningaxes for confining each of the X and Y sliders at opposite sides. Thisleads to a difficulty in improvement of the precision or enlargement ofthe stroke.

In the example of FIG. 11, on the other hand, if there is a tilt of abase table, for example, it may cause unwanted motion in the X or Ydirection. Furthermore, the arrangement itself cannot be used in avacuum ambience.

It is accordingly an object of the present invention to provide ahigh-precision stage system that can meet enlargement of the stroke.

In accordance with an aspect of the present invention, to achieve thisobject, there is provided a stage system, comprising a first fixed guidehaving a first guide surface being parallel to or approximately parallelto a first direction and a second direction being orthogonal to orapproximately orthogonal to the first direction, a first movable guideto be guided by the first fixed guide and having three freedoms ofmovement of straight motions in the first and second directions and amotion in a rotational direction about a third direction beingorthogonal to or approximately orthogonal to the first and seconddirections, the first movable guide having a first guide extending inthe second direction, a second fixed guide having a second guide surfacebeing parallel to or approximately parallel to the first and seconddirections, a second movable guide to be guided by the second fixedguide and having three freedoms of movement of straight motions in thefirst and second directions and a motion in a rotational direction aboutthe third direction, the second movable guide having a second guideextending in the first direction, and a central movable member to beguided in the first and second directions by means of the first andsecond guides.

In accordance with another aspect of the present invention, there isprovided a stage system comprising a first fixed guide having a firstguide surface being parallel to or approximately parallel to a firstdirection and a second direction being orthogonal to or approximatelyorthogonal to the first direction, a first movable guide to be guided bythe first fixed guide and having a first guide extending in the seconddirection, a second fixed guide having a second guide surface beingparallel to or approximately parallel to the first and seconddirections, a second movable guide to be guided by the second fixedguide and having a second guide extending in the first direction, athird fixed guide having a third guide surface being parallel to orapproximately parallel to the first and second guide surfaces, and acentral movable member to be guided in the first and second directionsby means of the first and second guides, and also to be guided by thethird fixed guide in a third direction being orthogonal to orapproximately orthogonal to the first and second directions, wherein thecentral movable member is attracted to the third fixed guide by means ofa permanent magnet unit having a magnetic shield.

In accordance with the present invention, a high-precision stage systemthat can meet enlargement of the stroke can be accomplished. Further,since the fixed guide (guide surface) is divided into plural guides,even if a magnetic preload is used, magnets can be magnetically shieldedeffectively. Thus, the stage system can be well incorporated into anelectron beam exposure apparatus.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a main portion of an electron beamexposure apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a main portion of a stage system in theFIG. 1 embodiment.

FIG. 3 is a diagram for explaining a stage control system of the stagesystem of the FIG. 2 example.

FIGS. 4A and 4B are schematic views for explaining operation of a linearmotor of the stage system of FIG. 2.

FIG. 5 is a schematic view of a stage system according to a secondembodiment of the present invention.

FIGS. 6A-6D are schematic views for explaining a base arrangement forsupporting sliders in the stage system of FIG. 2.

FIG. 7 is a schematic view for explaining another example of the basearrangement.

FIGS. 8A and 8B are schematic views, explaining a further example of thebase arrangement.

FIGS. 9A and 9B illustrate an exhaust system in the stage system of FIG.2.

FIG. 10 is a perspective view of a stage system of a first conventionalexample.

FIGS. 11A and 11B are schematic views, showing a stage system of asecond conventional example.

FIG. 12 is a schematic view of a general structure of a multipleelectron-beam exposure apparatus.

FIG. 13 is a schematic view for explaining the action as a wafer isscanned with a plurality of electron beams, in the exposure apparatus ofFIG. 12.

FIG. 14 is a flow chart for explaining device manufacturing processes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may take the following preferred forms.

That is, a stage system in one preferred form of the present inventioncomprises a first fixed guide (1 a, 1 c: reference numerals are thoseused in the embodiments to be described later), having a plane (firstguide surface) being parallel to or approximately parallel to a firstdirection (X direction) and a second direction (Y direction) beingorthogonal to or approximately orthogonal to the first direction, afirst movable guide (3) to be guided by the first fixed guide and havingthree freedoms of movement, including a motion in a rotational directionabout a third direction being orthogonal to or approximately orthogonalto the first and second directions (the first movable guide having aguide 3 f extending in the Y direction), a second fixed guide (1 b, 1 d)having a plane (second guide surface) being parallel to or approximatelyparallel to the first and second directions, a second movable guide (2)to be guided by the second fixed guide and having three freedoms ofmovement in the first, second and third directions (the second movableguide having a guide 2 f extending in the X direction, and a centralmovable member (4) to be guided in the X and Y directions by means ofthe Y guide 3 f and X guide 2 f.

Preferably, the stage system may further comprise (i) a first actuatorgroup (34 m) for driving the first movable guide (3) in three-freedom ofmovement directions (the first actuator group including a first Xactuator for driving the first movable guide in the X direction with arelatively long stroke, and a first Y actuator for driving the firstmovable guide in the second direction with a relatively short stroke),and (ii) a second actuator group (24 m) for driving the second movableguide (2) at least in two-freedom of movement directions of X and Y (thesecond actuator group including a second Y actuator for driving thesecond movable guide in the Y direction with a relatively long stroke,and a second X actuator for driving the second movable guide in the Xdirection with a relatively short stroke).

Moreover, preferably, the stage system may further comprise a thirdfixed guide (1) having a plane extending in the X and Y directions. Thecentral movable member (4) may be guided by the third fixed guide. Theupper surfaces of the first, second and third fixed guides, functioningas a guide surface, may be parallel to or approximately parallel to eachother. These guides may comprise a static pressure bearing. Theactuators may comprise a non-contact linear motor. On that occasion, thefirst X actuator may use a Y-direction magnetic flux component of apermanent magnet 134 mag group (X movable element), while the first Yactuator may use an X-direction magnetic flux component of the permanentmagnet group. The second Y actuator may use an X-direction magnetic fluxcomponent of a permanent magnet group (Y movable element), while thesecond X actuator may use a Y-direction magnetic flux component of thepermanent magnet group.

Moreover, the stage system may preferably further comprise a third fixedguide (1) having a plane in the X and Y directions, and the centralmovable member (4) may be guided by the third fixed guide. A firstmagnet (39) may apply a preload to the first movable guide (3) withrespect to the first fixed guide (1 a, 1 c), and a second magnet (29)may apply a preload to the second movable guide (2) with respect to thesecond fixed guide (1 b, 1 d). A third magnet (49) may apply a preloadto the central movable member (4) with respect to the third fixed guide(1). The first, second and third magnets may have magnetic shields (39sh, 29 sh, 49 sh), respectively.

When the magnetic resistance of a magnetic path defined inside eachmagnetic shield and the first, second and third magnets is Re, and themagnetic resistance of a magnetic path defined interactively between thefirst, second and third magnets is Rr, there may be a relation Re<Rr.

Preferably, the actuators may comprise non-contact linear motors, havinga magnetic shield. The first Y actuator or the second X actuator maycomprise an electromagnet.

A stage system in a second preferred form of the present inventioncomprises a first fixed guide (1 a, 1 c) having a plane (first guidesurface) being parallel to or approximately parallel to a firstdirection (X direction) and a second direction (Y direction) beingorthogonal to or approximately orthogonal to the first direction, afirst movable guide (3) to be guided by the first fixed guide (the firstmovable guide having a Y guide 3 f extending in the Y direction, asecond fixed guide (1 b, 1 d) having a plane (second guide surface)being parallel to or approximately parallel to the first and seconddirections, a second movable guide (2) to be guided by the second fixedguide (the second movable guide having an X guide 2 f extending in the Xdirection), a third fixed guide (1) having a third guide surface beingparallel to or approximately parallel to the first and second guidesurfaces, and a central movable member (4) to be guided in the X and Ydirections by means of the Y guide (3 f) and the X guide (2 f), and alsoto be guided by the third fixed guide (1) in a third direction beingorthogonal to or approximately orthogonal to the first and seconddirection, wherein the central movable member is attracted to the thirdfixed guide by means of a permanent magnet (1) unit having a magneticshield.

Preferred embodiments of the present invention will now be describedwith reference to the attached drawings.

FIG. 1 is a schematic view of a main portion of an electron beamexposure apparatus according to an embodiment of the present invention.Denoted in FIG. 1 at 300 is a vacuum sample chamber, and denoted at 301is an electron gun having a cathode 301 a, a grid 301 b and an anode 301c. Electrons emitted from the cathode 301 a produce a crossover imagebetween the grid 301 b and the anode 301 c (hereinafter, the crossoverimage will be referred to as a light source).

Electrons emitted from this light source are formed into anapproximately parallel electron beam by means of a condenser lens 302having a front focal point position placed at the light source position.The approximately parallel electron beam is then incident on an elementelectron optical system array 303. The element electron optical systemarray 303 includes a plurality of element electron optical systems eachcomprising a blanking electrode, an aperture and an electron lens. Theseelement electron optical systems are arrayed along a directionperpendicular to the optical axis of a reduction electron optical system100, which is parallel to the Z axis. Details of the element electronoptical system array 303 will be described later.

The element electron optical system array 303 functions to produce aplurality of intermediate images of the light source, and theseintermediate images are projected in a reduced scale by the reductionelectron optical system 100, whereby light source images are formed upona wafer 305. Here, the components of the element electron optical systemarray 303 are set so that the spacing of the light source images formedon the wafer 305 has a size corresponding to a multiple, by an integralnumber, of the size of the light source. Further, the element electronoptical system 303 functions to assure that the positions of the lightsource images with respect to the optical axis directions are differentin accordance with the field curvature of the reduction electron opticalsystem 100. Also, the element electron optical system functions tocorrect aberration to be produced as the intermediate images areprojected on the wafer 305 by the reduction electron optical system 100.

The reduction electron optical system 100 includes two-stage typesymmetric magnetic tablets, comprising a first projection lens (341,343) and a second projection lens (342, 344). When the focal length ofthe first projection lens (341, 343) is f1 while the focal length of thesecond projection lens (342, 44) is f2, the distance between these twolenses is equal to f1+f2.

The object point on the optical axis is at the focal point position ofthe first projection lens (341, 343), and the image point thereof isfocused on the focal point of the second projection lens (342, 344).This image is reduced at −f2/f1. Also, since the magnetic fields ofthese two lenses are determined so that they act in mutually oppositedirections, theoretically, except five aberrations of sphericalaberration, isotropic astigmatism, isotropic coma aberration, fieldcurvature aberration, and longitudinal chromatic aberration, theremaining Seidel's aberration and chromatic aberration concerningrotation and magnification can be cancelled.

Denoted at 306 is a deflector for deflecting plural electron beams fromthe element electron optical system array 303 so as to shift plurallight source images upon the wafer 305 in the X and Y directions by thesame displacement amount. While not shown in the drawing, the deflector306 comprises a main deflector to be used when the deflection width iswide, and a sub-deflector to be used when the deflection width isnarrow. The main deflector is an electromagnetic type deflector, whilethe sub-deflector is an electrostatic type deflector.

Denoted at 307 is a dynamic focus coil for correcting a deviation of thefocus position of the light source image, based on deflection aberrationto be produced when the deflector 306 is operated. Denoted at 308 is adynamic coil, which serves, like the dynamic focus coil 307, to correctastigmatism of deflection aberration to be produced by the deflection.Denoted at 99 is an alignment scope having an off-axis management, fordetecting a mark already formed on the wafer.

Denoted at 310 is a top stage for carrying a wafer 305 thereon. Forobservation of the whole surface of the wafer 305 through the alignmentscope 99, the top stage 310 should have a stroke corresponding to thewafer diameter, just underneath the alignment scope 99.

Denoted at 4 is an X-Y slider for carrying the top stage 310 thereon andbeing movable in the X and Y directions, which are orthogonal to theoptical axis (Z axis). The X-Y slider will be explained in greaterdetail, in conjunction with FIG. 2. The X-Y slider 4 comprises an X-Yslider-(y) 41 and an X-Y slider-(x) 42. At the bottom of the X-Yslider-(y) 41, there is a vacuum-proof bearing 43 disposed opposed tothe top face 1 f of a stage base 1. Also, inside the side wall of theX-Y slider-(y) 41, there is a similar vacuum-proof bearing 44 disposedto sandwich a Y guide 3 f.

Further, inside the side wall of the X-Y slider-(x) 42, there is asimilar vacuum-proof bearing 45 disposed to sandwich an X guide 2 f. TheY guide 3 f is formed at opposite side walls of the beam 32 (providing Xslider 3), in the lengthwise direction. The X guide 2 f is formed at theopposite side walls of a Y beam (providing Y slider 2), in thelengthwise direction. The X slider 3 having the Y guide 3 f and the Yslider 2 having the X guide 2 f are formed in a grid-like shape as shownin FIG. 3.

When the X-Y slider 4 is to be moved in the X direction, the X slider 3is moved in the X direction by which it can be moved smoothly along theX guide 2 f and the stage base top face 1 f. When the X-Y slider 4 is tobe moved in the Y direction, the Y slider 2 is moved in the Y directionby which it can be moved smoothly along the Y guide 3 f and the stagebase top face 1 f.

The Y slider 2 will now be explained. The Y slider 2 has a Y beam 22including the X guide 2 f, as well as a Y foot 21 and a Y foot 21′disposed on the opposite side with respect to the X direction. At thebottom of the Y foot 21 (21′), there is a vacuum-proof bearing 23disposed opposed to the top face of a beam base 1 b (1 d).

The top face of the beam base 1 b (1 d) is parallel to or approximatelyparallel to the stage base top face 1 f. The Y slider 2 can movesmoothly in the Y direction by a required stroke, within the range ofthe top face of the beam base 1 b (1 d), and also it can move smoothlyin the direction and a rotational direction about the Z axis(hereinafter, “Z-axis rotational direction”). Thus, the Y slider 2 canmove with a long stroke in the Y direction and with a short stroke inthe X direction. Thus, adding the Z-axis rotational direction, it canmove with three freedoms of movement.

Also, there are linear motor movable elements 24 m disposed at theopposite sides with respect to the X direction, for driving the Y slider2 in the Y direction. Each linear motor movable element 24 m contains apermanent magnet therein, and a magnetic shield cover is mounted thereonto prevent leakage of magnetic field into the stage space. A linearmotor for moving the Y slider 2 in the X direction is also housed in themovable element 24 m. Details will be described later, with reference toFIG. 4.

The Y foot 21 is provided with a reflection mirror 26 for measuring theposition in the Y direction and a reflection mirror 26 x for measuringthe position in the X direction, while the Y foot 21′ is provided with areflection mirror 26′ for measuring the position in the Y direction.Thus, by use of interferometer systems 126, 126′ and 126 x, the position(x, y, θz) of the Y slider 2 in the directions of X, Y and Z-axisrotation can be measured.

Similarly, the X slider 3 will now be described. The X slider 3 includesan X beam 32 having the Y guide 3 f, and an X foot 31 and an X foot 31′disposed on opposite sides with respect to the Y direction. At thebottom of the X foot 31 (31′), there is a vacuum-proof bearing 33disposed opposed to the top face of a beam base 1 a (1 c).

The top face of the beam base 1 a (1 c) is parallel to or approximatelyparallel to the stage base top face 1 f. The X slider can move smoothlyin the X direction by a required stroke, within the range of the topface of the beam base 1 a (1 c), and also it can move smoothly in the Ydirection and the Z-axis rotational direction. Thus, the X slider 3 canmove with a long stroke in the X direction and with a short stroke inthe Y direction. Thus, adding the Z-axis rotational direction, it canmove with three freedoms of movement. Also, there are linear motormovable elements 34 m disposed at the opposite sides with respect to theY direction, for driving the X slider in the X direction.

Each linear motor movable element 34 m contains a permanent magnettherein, and a magnetic shield cover is mounted thereon to preventleakage of a magnetic field into the stage space. A linear motor formoving the X slider in the Y direction is also housed in the movableelement 34 m.

The X foot 31 is provided with a reflection mirror 36 for measuring theposition in the X direction, while the X foot 31′ is provided with areflection mirror 36 y for measuring the position in the Y direction anda reflection mirror 36′ for measuring the position in the X direction.Thus, by use of interferometer systems 136, 136′ and 136 y, the position(x, y, θz) of the X slider 3 in the directions of X, Y and Z-axisrotation can be measured.

FIG. 3 is a diagram of a control system for the X and Y sliders. Thevalues of the interferometer systems 136, 136′ and 136 y correspondingto the X slider 3 are converted by an X slider computing unit 130 intothe X-direction position x, Y-direction position y and Z-axis rotationaldirection θz of the X slider 3, and they are applied as a feedbacksignal to an X slider controller 131. The X slider controller 131calculates a driver designated value (Xfx, Xfx′, Xfy) and, by applyingan electrical current to a coil array provided in an associated X stator34 s, driving forces Xfx and Xfx′ in the X and Z-axis rotationaldirections, as well as a driving force Xfy in the Y direction, areproduced.

Similarly, the values of the interferometer systems 126, 126′ and 126 xcorresponding to the Y slider 2 are converted by a Y slider computingunit 120 into the X-direction position x and Y-direction position y ofthe Y slider 2, and they are applied as a feedback signal to a Y slidercontroller 121. The Y slider controller 121 calculates a driverdesignated value (Yfy, Yfx) and, by applying an electrical current to acoil array provided in an associated Y stator 24 s, driving forces Yfyin the Y direction, as well as a driving force Yfx in the X direction,are produced. In the control system of this embodiment, the Z-axisrotation of the X slider 3 is controllably confined, while the Z-axisrotation of the Y slider 2 follows the rotation of the X slider 3.

As described above, three freedoms of movement of the X slider and twofreedoms of movement of the Y slider are controllably confined, by whichthree freedoms of movement of the X-Y slider 4 can be controlled. Here,the X-direction position of the X-Y slider 4 can be regarded as beingsubstantially equivalent to the X-direction position of the X slider 3,and the Y-direction position of the X-Y slider can be regarded as beingsubstantially equivalent to the Y-direction position of the Y slider 2.Also, the Z-axis rotation thereof can be regarded as being substantiallyequivalent to the Z-axis rotation of the X slider 3. Measurement forthese rough-motion sliders can be performed in various combinations and,as an example, the X-Y slider 4 can be measured directly by use of aninterferometer.

Further, while the positional information of the Y slider 2 regardingthe rotational direction is not specifically used in this embodiment asa measured value, a control may be added by using velocity informationin the rotational direction.

Referring now to FIGS. 4A and 4B, the linear motor to be used in thepresent invention will be explained while taking the linear motor 34 ofthe X slider 3 as an example. As described hereinbefore, the linearmotor 34 has a movable element 34 m and a stator 34 s. The movableelement 34 m comprises a movable magnet 134 mag and a magnetic shield134 sh. The stator 34 comprises coil arrays 134 a, 134 b, 134 c, 134 dand 134 e, which are disposed along the stroke direction. Each coil hasa two-layer structure. There is a jacket 134 j for covering the coilarrays, to prevent the coil arrays from being bared inside the vacuumsample chamber. The movable magnet 134 mag includes X-directionmagnetized magnets, which are alternately sandwiched between Y-directionmagnetized magnets, to provide a magnetic flux distribution near a sinewave in the coil space.

FIG. 4A illustrates a state in which a driving force acts in the Xdirection. A Y-direction largest magnetic flux By is being produced atthe coil b. At this moment, by supplying electrical currents of the samephase to the coils 134 b _(—) u and 134 b _(—) d, due to the Lorentz'sforce, a force is applied to the movable element 34 m in the Xdirection.

FIG. 4B illustrates a state in which a driving force acts in the Ydirection. An X-direction largest magnetic flux Bx is being produced atthe coil c, in opposite directions at the positions of the coils 134 b_(—) u and 134 b _(—) d. At this moment, by applying electrical currentsof opposite phases to the coils 13 b _(—) u and 134 b _(—) d, due to theLorentz's force, a force is applied to the movable element 34 m in the Ydirection. Although this force in the Y direction may be weak ascompared with the force in the X direction, there does not occur aparticular problem since the force in the Y direction is not used foracceleration of the X slider.

FIG. 5 illustrates an electromagnet arrangement, as a second embodiment,for applying a driving force in the Y direction for the X slider and adriving force in the X direction for the Y slider. The X foot 31 and Xfoot 31′ of the X slider 3 are provided with a linear motor movableelement 34 m″ for applying an X-direction driving force and,additionally, the X foot 31′ is provided with an electromagnet unit 34m′ for applying a Y-direction driving force. The electromagnet unit 34m′ includes an E-shaped core 234EM, a coil 234 co and a magnetic shield234 sh, at the movable side, which are fixed to the X foot 31′ by anon-magnetic material 235. Also, there is a magnetic material bar 234Iat the fixed side, which is fixed to the beam base 1 c by a non-magneticmaterial 236. In the electromagnetic unit 34 m′, the X slider 3 can bedriven in the Y direction by selectively applying and controlling avoltage to opposed coils.

The Y foot 21 and the Y foot 21′ of the Y slider 2 are provided with alinear motor movable element 24 m″ for applying a Y-direction drivingforce and, additionally, the Y foot 31′ is provided with anelectromagnet unit 24 m′ for applying an X-direction driving force. Theelectromagnet unit 24 m′ includes an E-shaped core 224EM, a coil 224 coand a magnetic shield 224 sh, at the movable side, which are fixed tothe Y foot 21′ by a non-magnetic material 235. Also, there is a magneticmaterial bar (I-shaped core) 224I at the fixed side, which is fixed tothe beam base 1 d by an I-shaped core mounting member 236 made of anon-magnetic material. In the electromagnetic unit 24 m′, the Y slider 2can be driven in the X direction by selectively applying and controllinga voltage to opposed coils.

Referring now to FIGS. 6A-6D, the structure at the bottom faces of thesliders will be explained. FIG. 6A illustrates the whole structure asviewed from the bottom, for explaining the base arrangement forsupporting the sliders. FIG. 6B illustrates a single bottom pad. As hasbeen described with reference to FIG. 2, at the bottom of the X-Yslider-(y) 41, there is a vacuum-proof bearing 43 disposed opposed tothe top surface 1 f of the stage base 1. At the bottom of the Y foot 21(21′), there is a vacuum-proof bearing 23 disposed opposed to the topsurface of the beam base 1 b (1 d). At the bottom of the X foot 31(31′), there is a vacuum-proof bearing 33 disposed opposed to the topsurface of the beam base 1 a (1 c). Details of such pads are such asshown in FIG. 6B. Specifically, each pad comprises a static-pressurebearing portion 51 in which a fluid is discharged through a porousmaterial, a labyrinth portion 52 for preventing leakage of thedischarged fluid into the ambience, and an exhaust bore 53. Thelabyrinth portion includes a plurality of lands 52L and grooves 52 g,for providing a fluid resistance without contact.

In order to attain a desired rigidity in a static-pressure bearing,generally, a preload is applied to the static-pressure bearing. In thisembodiment, a preload is applied on the basis of an attraction force ofa permanent magnet. The preload application may be made by a simplefloat-type preload such as a vacuum preload (in a case wherein theambience is at atmosphere or a reduced pressure ambience) or a magnetpreload, or a confinement type load in which a preload is applied whilea static-pressure bearing is disposed opposed.

In this embodiment, since the system is used in a vacuum ambience, thesimple float-type preload based on a magnet preload is used. In FIG. 6,denoted at 29 is a permanent magnet fixed to the Y foot, and denoted at39 is a permanent magnet fixed to the X foot. Denoted at 49 is apermanent magnet fixed to the X-Y slider-(y) 41 (FIG. 2). These magnetsare covered by magnetic shields 29 sh, 39 sh and 49 sh, for preventingleakage of their magnetic shield. Since the confinement-type preload isnot used, only the bearing surface and the guide surface are theprecision required surface.

On the other hand, a structure such as a confinement-type preload isused as shown in FIG. 2, that is a vacuum-proof bearing 45 is providedat the opposite sides of the inside wall of the X-Y slider-(x) 42 tosandwich the opposed X guide 2 f therebetween. On that occasion,regarding the precision required surface, the parallelism of theopposite sides of the bearing 45 at the X-Y slider side, as well as theparallelism of the opposite faces of the X guide 2 f, should becontrolled. However, the rigidity will be improved in this case.

Further, when permanent magnets are used in an electron beam exposureapparatus as in the present embodiment, in addition to covering eachpermanent magnet by use of a magnetic shield, the following measures maybe done. That is, in FIG. 6A, the bases (1, 1 a, 1 b, 1 c, 1 d) ofmagnetic materials, which are the object to be attracted by therespective permanent magnets, are magnetically isolated from each other.

More specifically, the preload magnet 49 of the X-Y slider is disposedopposed to the stage base 1, and the preload magnet 29 of the Y slideris disposed opposed to the beam base 1 b (1 d). The preload magnet 39 ofthe X slider is disposed opposed to the beam base 1 a (1 c). The bases1, 1 a, 1 b, 1 c and 1 d of them are disposed with a certain mutualmagnetic resistance.

The effect of this structure will be explained, in conjunction withFIGS. 6C and 6D. FIG. 6C shows a case wherein the bases are notmagnetically isolated, and FIG. 6D shows a case wherein the bases areisolated. If they are not isolated, in addition to magnetic circuits L1produced by the respective magnets, a magnetic circuit L2 is producedbetween plural magnets and this leaks outwardly beyond the shields 29sh, 39 sh and 49 sh. On the other hand, if magnetic isolation isprovided (that is, the magnetic resistance is enlarged sufficientlyhigh), the magnetic flux leakage between plural magnets can be reducedas much as possible.

FIG. 7 illustrates the base arrangement according to a secondembodiment, as viewed from the bottom. In FIG. 7, the base 1′ to whichthe respective permanent magnets are disposed opposed is formedintegrally. There is a slit Is between movable regions of the sliders,to increase the magnetic resistance between plural magnets, such thatmagnetic flux leakage to be produced between plural magnets isminimized. In the arrangement of FIG. 7, the precision setting at theguide surface 1 f of the base 1′ is easy.

FIG. 8A shows the base arrangement according to a third embodiment, asviewed from the bottom. In FIG. 8A, in the bottom pad movable region ofeach slider, a common base 1″ and the magnetic material base 1 m towhich the permanent magnets 29 and 29 of the sliders 2 and 3 aremagnetically isolated from each other.

FIG. 8B illustrates the Y foot 21 as seen from the side thereof. TheY-bottom pad 23, including a labyrinth portion, uses the top face 1 f ofthe common base 1″ as a guide surface. The attracting permanent magnet29 for applying a preload to the Y-bottom pad 23 and the magnetic shield29 sh are disposed opposed to the magnetic material base 1m beingmagnetically isolated from the common base 1″,

As shown in FIG. 8A, while the attracting magnet of the X-Y slider 4 isdisposed opposed to the common base 1″, since the common base 1″ and themagnetic material base 1 m are magnetically isolated from each other,magnetic flux leakage to be produced between plural magnets can bereduced as much as possible. Furthermore, generally, the flatnessprecision may be looser at the surface opposed to the permanent magnetthan at the surface to be opposed to the bearing portion, and,therefore, the arrangement is advantageous with respect to machining andassembling.

FIGS. 9A and 9B are schematic views for explaining the flow of fluidscollected by exhaust bores 53′ and 53″ of lateral pads 44 and 45 of theX-Y slider 4. In the electron beam exposure apparatus according to thisembodiment of the present invention, as has been described withreference to FIGS. 1 and 2, an alignment scope 99 is disposed in the Xdirection such that, for observation of the whole surface of the waferthrough the alignment scope, the top stage should have a stroke, justbelow the alignment scope, that corresponds to the wafer diameter. Thedistance from the center of the projection optical system to thealignment scope is called a “base line”, and, in this arrangement, theX-direction stroke Xst is longer than the Y-direction stroke Yst by thebase line (i.e., Xst>Yst). Thus, the following measures are taken, inthis embodiment.

The fluid discharged from the Y lateral pad 45 is collected by theexhaust bore 53′ formed in the labyrinth portion grooves 52 g (FIG. 6).The collected fluid is discharged to the labyrinth portion groove 52 gof the X lateral pad 44 through a pipe 55 provided in the X-Y slider 4and the X lateral pad 44. The thus discharged fluid and the fluiddischarged from the X lateral pad 44 are mixed with each other. The thuscombined fluid is collected through an exhaust bore 53″ formed in the Xbeam 32. The collected fluid is discharged outwardly of the vacuumsample chamber 300 (FIG. 1) through a pipe 56 formed in the X beam 32and the X foot 31 (31′) and from a flexible tube 38 connected to the Xfoot 31 (31′).

The labyrinth portion groove 52 g of the Y lateral pad 44 should have alength the same as or larger than the Y-direction stroke Yst. Althoughthe X-direction stroke is still longer, since, in this embodiment, thefluid discharged from the X lateral pad 45 is collected at the X-Yslider 4 side, it is not necessary for the labyrinth portion groove 52 gof the X lateral pad to have a length the same as the X-direction strokeXst. Therefore, the size of the X-Y slider structure including thelateral pads 44 and 45 can be held to be small.

Next, semiconductor device manufacturing processes using an exposureapparatus described above, will be explained.

FIG. 13 is a flow chart for explaining a general procedure formanufacturing semiconductor devices. Step 1 is a design process fordesigning a circuit of a semiconductor device. Step 2 is a process formaking a mask on the basis of the circuit pattern design. Step 3 is aprocess for preparing a wafer by using a material such as silicon. Step4 is a wafer process, which is called a pre-process, wherein, by usingthe thus prepared mask and wafer, a circuit is formed on the wafer inpractice, in accordance with lithography. Step 5 subsequent to this isan assembling step, which is called a post-process, wherein the waferhaving been processed at step 4 is formed into semiconductor chips. Thisstep includes an assembling (dicing and bonding) process and a packaging(chip sealing) process. Step 6 is an inspection step wherein anoperation check, a durability check, and so on, for the semiconductordevices produced by step 5, are carried out. With these processes,semiconductor devices are produced, and they are shipped (step 7).

Step 4 described above includes an oxidation process for oxidizing thesurface of a wafer, a CVD process for forming an insulating film on thewafer surface, an electrode forming process for forming electrodes uponthe wafer by vapor deposition, an ion implanting process for implantingions to the wafer, a resist process for applying a resist(photosensitive material) to the wafer, an exposure process forprinting, by exposure, the circuit pattern of the mask on the waferthrough the exposure apparatus described above, a developing process fordeveloping the exposed wafer, an etching process for removing portionsother than the developed resist image, and a resist separation processfor separating the resist material remaining on the wafer after beingsubjected to the etching process. By repeating these processes, circuitpatterns are superposedly formed on the wafer.

Although the foregoing description has been made with reference toexamples in which the present invention is applied to an electron beamexposure apparatus, with appropriate modification of the structure, thepresent invention can be applied to a vacuum-ambience exposure apparatusthat does not use an electron beam, for example, an EUV exposureapparatus in which EUV (extreme ultraviolet) light is used as exposurelight. Furthermore, the stage of the present invention can be used notonly in a vacuum, but also in a desired gas ambience.

If an electron beam is not used, since it is not necessary to considerthe problem of a change in magnetic field in that case, there is nonecessity of providing a magnetic shield to the linear motor or thepermanent magnet. Further, it is unnecessary to magnetically isolate thebase tables (bases) from each other.

On the other hand, even in an electron beam exposure apparatus, when theX slider and/or the Y slider is made on the basis of theconfinement-type preload as described hereinbefore, it is not necessaryto magnetically isolate the base tables from each other.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

1. A stage system, comprising: a first fixed guide having a first guidesurface being parallel to or approximately parallel to a first directionand a second direction being orthogonal to or approximately orthogonalto the first direction; a first movable guide to be guided by said firstfixed guide and having three freedoms of straight motions in the firstand second directions and a motion in a rotational direction about athird direction being orthogonal to or approximately orthogonal to thefirst and second directions, said first movable guide having a firstguide extending in the second direction; a second fixed guide having asecond guide surface being parallel to or approximately parallel to thefirst and second directions; a second movable guide to be guided by saidsecond fixed guide and having three freedoms of straight motions in thefirst and second directions and a motion in a rotational direction aboutthe third direction, said second movable guide having a second guideextending in the first direction; and a central movable member to beguided in the first and second directions by means of said first andsecond guides. 2-15. (canceled)